Physical principles are basic to an analysis of peristaltic function and sphincter competence in the gastrointestinal and genitourinary tracts. Peristalsis is produced by a coordinated muscular activity which changes luminal dimensions and pressure in a patterned way. Sphincter competence depends on tonic contracture of the sphincter muscles, which is inhibited during the peristaltic sequence. An adequate knowledge of the structural and physiological characteristics of the gastrointestinal and genitourinary tracts is necessary for the evaluation of normal peristaltic function and of pathologic conditions leaging to derangements in motility, obstruction and reflux. Using previously developed and available techniques we plan to study the effect of stretch, pharmacologic agents, and electrical stimulation, on in vivo and in vitro, normal and abnormal portions of the gastrointestinal and genitourinary tracts. The relationships between intraluminal pressure, length, diameter, circumferential and longitudinal forces, stress, strain and velocity of contraction will be investigated in order to define the factors which govern normal behavior, and to determine how these factors are modified in pathologic conditions. Using these modalities we will assess some mechanical and surgical procedures which alter the mechanical characteristics of the gastrointestinal and genitourinary tract. The long term goal of these studies is to define the mechanical characteristics of the whole gastrointestinal and genitourinary tracts. The strength of this group of investigators derives from diverse individual expertise and ability to work together. The techniques developed in previous funding periods are applicable and useful, not only to define functional characteristics of single organs, but may be used to analyze mechanical behavior of the whole digestive and urinary tract. This we propose to do in the course of succeeding funding periods.